ALM-173-R1 Alarm Systems

Overview

The ALM-173-R1 is a modular alarm I/O device featuring 17 opto-isolated inputs, 3 SPDT relays, and local buttons and LEDs. It connects via RS-485 (Modbus RTU) to a MicroPLC, MiniPLC, or any compatible controller, and can integrate with Home Assistant (ESPHome) or SCADA/PLC systems. Configuration is performed through a driverless Web Serial interface via USB-C, using the browser-based WebConfig Tool. The module supports both master-controlled and standalone local logic modes, with configurable alarm groups and acknowledgment logic.

Getting Started

Quick Setup Process

1. Mount & Wire – Install on 35mm DIN rail, connect 24V DC power, sensors, and relay loads.

2. Configure – Plug in USB-C, open the WebConfig tool in Chrome/Edge, set Modbus address and I/O mapping.

3. Integrate – Connect to your controller via RS-485 and start automation.

What You Need

• ALM-173-R1 module

• 24 VDC SELV power supply

• RS-485 cable (twisted pair)

• USB-C cable for configuration

• Chromium-based browser (Chrome/Edge)

Web Configuration Steps

1. Connect USB-C to module and PC

2. Open https://www.home-master.eu/configtool-alm-173-r1

3. Click "Connect" and select serial port

4. Set Modbus address (default: 3) and baud rate (default: 19200 8N1)

5. Configure input actions, relay mapping, LED modes, and button functions

6. Settings save automatically to flash

Tech Specs

Documentation

The DIO-430-R1 is open-source hardware! You can build your own board using the following files:

Hardware Design Files

• MCU Board Schematic: ALM-173-R1-MCUBoard.pdf

• Field Board Schematic: ALM-173-R1-FieldBoard.pdf

• System Block Diagram: ALM_SystemBlockDiagram.png

• MCU Pinout Diagram: ALM_MCU_Pinouts.png

• Field Board Layout: FieldBoard-Diagram.png

• MCU Board Layout: MCUBoard-Diagram.png

Firmware & Software

• Firmware Source Code: ALM-173-R1/Firmware/

• WebConfig Tool: ConfigToolPage.html

• ESPHome Integration Package: default_alm_173_r1_plc.yaml

Mechanical Files

• Dimensional Drawing: ALMMDimensions.png

All design files and documentation are available in the HomeMaster GitHub repository.

Input and Output

Digital Inputs (17 channels)

• Opto-isolated inputs with TVS/PTC protection

• Per-channel settings: Enable, Invert, Alarm Group (1/2/3/None)

• Configurable debounce and latching logic

Relay Outputs (3 channels)

• SPDT contacts (NO/NC/COM)

• 16 A @ 250 V AC rating

• Individual enable/invert settings

• Can follow alarm groups, Modbus commands, or manual override

Alarm Groups

• 3 independent alarm groups + “Any Alarm” summary

• Modes: Active-while, Latched-until-acknowledged

• Local acknowledgment via buttons or Modbus

User Interface

• 4 Buttons: Configurable for acknowledgment or relay override

• 4 LEDs: Configurable steady/blink modes, linked to alarm groups or relay state

• Status LEDs: PWR, TX/RX (Modbus activity)

Communication Interfaces

• Protocol: Modbus RTU

• Role: Slave device

• Default Settings: Address 3, 19200 baud, 8 data bits, No parity, 1 stop bit

• Supported Functions: Read Coils (0x01), Read Discrete Inputs (0x02), Read Holding Registers (0x03), Read Input Registers (0x04), Write Single Coil (0x05), Write Single Register (0x06)

Modbus Address Map

Coils (Read/Write) - Function Codes 0x01, 0x05

Discrete Inputs (Read Only) - Function Code 0x02

Holding Registers (Read/Write) - Function Codes 0x03, 0x06

Home Assistant & ESPHome Integration Guide

Overview

The ALM-173-R1 integrates seamlessly with Home Assistant via ESPHome using the Modbus RTU protocol. This guide covers both quick integration using our pre-built package and manual configuration for advanced users.

Prerequisites

Before starting, ensure you have:

1. ESPHome device (HomeMaster MiniPLC/MicroPLC or any ESP32/ESP8266 with RS-485)

2. RS-485 connection between ESP device and ALM-173-R1

3. 24V power to ALM-173-R1 module

4. Home Assistant with ESPHome add-on installed

Configure Your ESPHome Device

Add this to your ESPHome YAML configuration:

# RS-485 Configuration
uart:
  id: uart_modbus
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 19200
  parity: NONE
  stop_bits: 1

modbus:
  id: modbus_bus
  uart_id: uart_modbus

packages:
  alm_1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: ALM-173-R1/Firmware/default_alm_173_r1_plc/default_alm_173_r1_plc.yaml
        vars:
          alm_prefix: "Security Panel"
          alm_id: security_module
          alm_address: 3
    refresh: 1d

Customize Variables

• alm_prefix: Appears in entity names (e.g., "Staircase Relay 1")

• alm_id: Must be unique if adding multiple ALM modules

• alm_address: Set to match your ALM-173-R1 Modbus address (default: 3)

Multiple ALM Modules

For additional modules, duplicate the package block with unique IDs:

packages:
  alm_zone1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: ALM-173-R1/Firmware/default_alm_173_r1_plc/default_alm_173_r1_plc.yaml
        vars:
          alm_prefix: "Zone1"
          alm_id: zone1_module
          alm_address: 5

  alm_zone2:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: ALM-173-R1/Firmware/default_alm_173_r1_plc/default_alm_173_r1_plc.yaml
        vars:
          alm_prefix: "Zone2"
          alm_id: zone2_module
          alm_address: 6

Programming

Supported Development Environments

• Arduino IDE with RP2350 support

• PlatformIO with RP2350 toolchain

• MicroPython (community builds available)

Firmware Flashing

1. Connect USB-C to PC

2. Hold Buttons 3 + 4 to enter BOOT mode

3. Hold Buttons 1 + 2 to RESET the module

4. Upload via:

   • UF2 drag-and-drop to mounted drive, OR

   • PlatformIO/Arduino IDE upload

Pin Mapping (Default Firmware)